Shearing force (friction) applied to a human body is one of the causes of a bedsore. For example, when a bed is inclined, shearing force occurs between a human body and the bed, thereby causing a bedsore in some cases.
In recent years, an attempt has been made to embed a force sensor for detecting shearing force in bedding such as an anti-bedsore mattress to detect the shearing force occurring between a human body and the bedding (e.g., see WO2003/079898).
The conventional technique described above, however, has a room for further improvement in that the shearing force can be detected with a simpler structure.